This invention relates to powder-free rubber articles produced by latex dipping and to the methods and materials used in their manufacture. More particularly, the invention relates to the production of powder-free natural and synthetic rubber latex medical articles, such as surgical and medical gloves, condoms and catheters, by employing a powder-free coagulant during fabrication.
The manufacture of a typical latex surgical glove generally requires latex and powders, as well as water, vulcanizing agents, accelerators, activators, blockers, retarders, antioxidants, preservatives, odorants, colorants, stabilizers, and other processing aids. The powder serves two important functions in the manufacture and use of latex gloves and other productsxe2x80x94it facilitates the release of a glove from a glove former during manufacture and it aids the donning of the gloves during use.
Gloves are manufactured by dipping ceramic or aluminum glove formers shaped like hands into tanks of liquid latex and admixed chemicals. The formers are precoated with a coagulant to gel the latex and to facilitate the subsequent removal of the glove from the former. The precoated formers are then dipped in the tanks of chemicals necessary to make the gloves. The xe2x80x9cwetxe2x80x9d gloves are dried and cured in a heated oven and the latex glove cures on the mold. The outside layer of the dipped former will ultimately be the inside of the glove. While still on the formers, the latex gloves also go through one or more rinses to leach out proteins and residual chemicals before they are stripped off the mold, packaged, and sterilized. The latex contains vulcanization agents that cure the natural rubber and produce a dry rubber film. Thus, the film surface of the cured natural rubber is quite xe2x80x9ctackyxe2x80x9d after the Clove is dried. It is therefore necessary to incorporate detackifying powders in the manufacturing process to facilitate the release of a glove from its glove former. Powders are also used to aid the donning of the gloves.
The use of powder complicates the manufacturing process and may cause respiratory problems for workers during the manufacturing process. Likewise, powder can be released into the air and inhaled when medical or health care personnel don and remove their gloves during subsequent use.
In order to reduce the likelihood of such problems, it is common practice for health care personnel to remove excess powder from the gloves after donning by wiping gloves thoroughly with a sterile sponge or sterile towel. Similarly, manufacturers attempt to minimize the amount of powder on the gloves they manufacture by including additional manufacturing steps in the glove fabrication process. For example, some manufacturers subject the fabricated gloves to air-blowing or tumbling operations to remove excess powder. Other processes include encapsulation of the powder in the gloves by dipping the formed glove in a laminate material having better donning properties than the base rubber. Yet other processes halogenate the formed gloves to remove the powder and create a smooth glove surface.
Each of the foregoing processes reduce, but do not eliminate, the problems associated with the use of powdered gloves. As a result, one process completely eliminates the use of powder. U.S. Pat. No. 4,548,844 to Podell et al. discloses a powder-free article made by conventional dipping techniques. However, Podell et al. eliminates the use of powder only by using a manufacturing process substantially more complex than that of the prior art. Whereas the prior art rendered glove surfaces tack-free by washing the finished gloves in a slurry of powder, Podell et al. achieved a powder-free glove only by washing the finished glove (i.e., after removal from the former) in a surfactant or an emulsion such as an aqueous silicone solution, and drying the washed glove in a heated oven prior to a final rinse in water. Moreover, the surfactant or emulsion was effective to eliminate tack only if further steps, such as dipping the former in acid and a hydrophilic polymer, were taken prior to vulcanizing the glove and removing it from the formers. Thus, Podell et al. does not render the manufactured glove tack-free until after the glove is removed from the former on which it is made.
Because powder is used in glove manufacturing processes in order to facilitate removal of the gloves from the glove formers, such powder-free gloves are difficult to remove from their formers because they are tacky. The process required to strip such gloves is much more complicated or labor intensive and also more time consuming than it would be if the gloves on the formers were tack-free. For example, because the gloves manufactured according to Podell et al. were still tacky while on the formers, they had to be removed from their formers by manual labor. Many gloves are lost because they stick to the formers and are damaged during the removal process. It is therefore desirable to have a powder-free, tack-free glove that has good donning properties, that can be easily stripped from the glove formers following fabrication and that can be manufactured with a minimum number of processing steps.
The present invention solves the foregoing problems by providing a powder-free glove that is readily removable from the glove former following glove fabrication. The present invention also provides a powder-free coagulant and a glove fabrication process that includes that powder-free coagulant.
Accordingly, it is an object of the present invention to provide powder-free rubber articles produced by latex dipping.
It is another object of the present invention to provide a powder-free glove that can be easily stripped from the glove formers following fabrication.
A further object of the present invention is to provide such powder-free rubber articles that are durable and provide cut and abrasion protection.
The foregoing and additional objects are realized in the present invention that provides a powder-free coagulant composition for natural rubber latex. The coagulant composition includes an aqueous, salt stable polymer dispersion and at least one inorganic metal salt.
According to another embodiment of the present invention the coagulant composition may be employed in combination with a surfactant, a release agent, such as polypropylene wax, and a cationic surface active agent.
According to a further aspect of the present invention, a method of preparing a rubber article is provided that includes the steps of: dipping a shaped, pre-heated former into an aqueous, powder-free solution which comprises an aqueous, salt stable polychloroprene dispersion and an inorganic metal salt; dipping the former in a dispersion of a natural rubber latex to form a gelled latex film and to create a tack-free surface for the article; leaching the gelled latex film; curing the formed rubber article on the former; and dry stripping the cured tack-free article from the former.
Articles produced in accordance with the invention include those produced by conventional latex dipping processes, such as medical and surgical gloves, condoms and catheters.